Atmospheric Signal Propagation
Kapitel i bok, 2017
Global navigation satellite system (GNSS ) satellites emit signals that propagate as electromagnetic waves through space to the receivers which are located on or near the Earth’s surface or on other satellites. Thereby, electromagnetic waves travel through the ionosphere and the neutral atmosphere (troposphere) which causes signals to be delayed, damped, and refracted as the refractivity index of the propagation media is not equal to one. In this chapter, the nature and effects of GNSS signal propagation in both the troposphere and the ionosphere, aref examined. After a brief review of the fundamentals of electromagnetic waves their propagation in refractive media, the effects of the neutral atmosphere are discussed. In addition, empirical correction models as well as the state-of-the-art atmosphere delay estimation approaches are presented. Effects related to signal propagation through the ionosphere are dealt in a dedicated section by describing the error contribution of the first up to third-order terms in the refractive index and ray path bending. After discussing diffraction and scattering phenomena due to ionospheric irregularities, mitigation techniques for different types of applications are presented.